As the plane comes in to land, onlookers can be heard clapping while the captain says in German that Air Berlin will "cease it long-distance flights tomorrow" before thanking the traffic controllers he had worked with over the years.

German media said the manoeuvre was the pilot's unique way of saying "goodbye" to his passengers and the bankrupt airline, as it was Air Berlin's last long-haul flight to its hub in Dusseldorf. This was the last Air Berlin global flight out of the United States.

"We are awaiting the results of an internal investigation at Air Berlin", a spokesman for the watchdog said, without providing further details.

However, another video of the landing taken from the airport's control tower shows the risky move was actually an orchestrated flight path, despite airport employees fearing it would crash, The Sun reported.

"When he did this maneuver, I think nobody was scared because everybody [knew] what happened", Siegmayer said, adding that as a passenger, "I also liked it".

In the video, aviation enthusiasts are watching the plane coming in to land. German peer carrier Lufthansa is now in the process of buying up large parts of the bankrupt airline, and signed a deal last week for 210 million euros, or about $248 million.